This invention relates to polymerization catalysts, process for making catalysts and polymerization processes employing the catalysts.
In the field of catalytic polymerization of olefins such as ethylene to produce useful solid polymers, a continuing objective is to improve the bulk density of the polymer obtained from the catalyst and to reduce the amount of polymer fines produced in the polymerization process. In order to solve the problems of low polymer bulk density and the production of polymer fines, it is necessary to control the particle size as well as the particle size distribution of the catalyst support employed. When employing a milled catalyst support, such as for example, MgCl.sub.2 and/or AlCl.sub.3, a fine milled product is generally obtained because of the brittleness of such support materials.